More Details: A rotary hammer is a power tool that can perform heavy-duty tasks such as drilling and chiselling hard materials. It is similar to a hammer drill in that it also pounds the drill bit in and out while it is spinning. However, rotary hammers use a piston mechanism instead of a special clutch. This causes them to deliver a much more powerful hammer blow, making it possible to drill bigger holes much faster. SDS Plus is an improvement on the original SDS system, but remains compatible with SDS bits, and is now the most commonly seen on the market.